Conductive copper paste

Abstract

A conductive copper paste contains copper powder and a glass frit of a zinc borosilicate system as a solid component dispersed in an organic vehicle. The content of said glass frit in the solid component falls in a range of 0.5 to 8 percent by weight. The paste is applied to ceramic green sheets and fired simultaneously with the ceramic green sheets to provide copper coatings on the ceramic sheets.

What is claimed is: 
     
       1. A conductive copper paste for formation of copper coatings on ceramic substrates, the conductive copper paste consisting essentially of a solid component dispersed in an organic vehicle, the solid component consisting essentially of about 0.5 to 8 percent by weight of a zinc borosilicate glass frit and the remainder of a copper powder, the glass frit consisting essentially of about 40 to 50% by weight of B 2  O 3 , about 5 to 20% by weight of SiO 2  and about 30 to 40% by weight of ZnO. 
     
     
       2. The conductive copper paste according to claim 1 in combination with a ceramic substrate wherein the ceramic substrate is made of a BaO.Al 2  O 3 .SiO 2  system. 
     
     
       3. The conductive copper paste according to claim 1 wherein the conductive copper paste consists essentially of, by weight, about 73.6 to 79.6% copper powder, about 0.4 to 6.4% glass frit, and the remainder of an organic binder. 
     
     
       4. The conductive copper paste according to claim 1 wherein the copper powder has a particle size of about 0.1 to 5 μm. 
     
     
       5. A method of forming a conductive coating on a ceramic substrate, comprising the steps of: (a) dispersing a copper powder and about 0.5 to 8 percent by weight of a glass frit of a zinc borosilicate system in an organic vehicle to prepare a conductive copper paste;   (b) applying the resultant conductive copper paste on a ceramic substrate made of a BaO.Al 2  O 3 .SiO 2  system; and,   (c) firing the ceramic substrate coated with the conductive copper paste in a non-oxidizing atmosphere.   
     
     
       6. The method according to claim 5 wherein the glass frit consists essentially of about 40 to 50% by weight of B 2  O 3 , about 5 to 20% by weight of SiO 2  and about 30 to 40% by weight of ZnO. 
     
     
       7. A conductive copper paste for formation of a copper coating on a ceramic substrate, the conductive copper paste comprising a solid component dispersed in an organic vehicle, the solid component including about 0.5 to 8 percent by weight of a zinc borosilicate glass frit and a copper powder, the glass frit including about 40 to 50% by weight of B 2  O 3 , about 5 to 20% by weight of SiO 2  and about 30 to 40% by weight of ZnO. 
     
     
       8. The conductive copper paste according to claim 7 in combination with a ceramic substrate wherein the ceramic substrate is made of a BaO.Al 2  O 3 .SiO 2  system. 
     
     
       9. The conductive copper paste according to claim 7 wherein the conductive copper paste includes, by weight, about 73.6 to 79.6% copper powder, about 0.4 to 6.4% glass frit, and an organic binder. 
     
     
       10. The conductive copper paste according to claim 7 wherein the copper powder has a particle size of about 0.1 to 5 μm. 
     
     
       11. The method according to claim 5 wherein the glass frit includes about 40 to 50% by weight of B 2  O 3 , about 5 to 20% by weight of SiO 2  and about 30 to 40% by weight of ZnO.